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Date:	Fri, 18 Sep 2015 22:23:46 -0700
From:	"Darrick J. Wong" <>
To:	Dave Chinner <>
Cc:	Andreas Dilger <>, Johan Harvyl <>,
	"Theodore Ts'o" <>,
	"" <>
Subject: Re: resize2fs: Should never happen: resize inode corrupt! - lost key

On Sat, Sep 19, 2015 at 12:47:25PM +1000, Dave Chinner wrote:
> On Wed, Sep 16, 2015 at 07:21:59PM -0600, Andreas Dilger wrote:
> > If you add "-b 1024" to the mke2fs command line to use 1KB instead of 4KB blocks, and reduce the sizes by a factor of 4 does the problem still happen? That would make it easier for someone else to test, since it would only need a 4-5TB disk instead of a 19Tb array. 
> Sparse files on XFS using loopback will allow you to simulate
> devices larger than 16TB easily. You can turtle it all the way down,
> too, to create the xfs filesystem on a loopback device on a sparse
> file on ext4....
> Doing this sort of thing lets me know, for example, that the
> mkfs.ext4 defaults fail on a 500TB device...
> # xfs_io -f -c 'truncate 500t' /mnt/xfs/fs.img
> # ls -lh /mnt/xfs
> total 0
> -rw------- 1 root root 500T Sep 19 12:41 fs.img
> # mkfs.ext4 /mnt/xfs/fs.img
> mke2fs 1.42.13 (17-May-2015)
> /mnt/xfs/fs.img: Cannot create filesystem with requested number of inodes while setting up superblock

Whee.  I guess one would need to turn on meta_bg at mkfs time (which scatters
the group descriptors across the disk instead of (failing to) sandwich them in
a single blockgroup... and fix the overhead calculation in ext2fs_initialize to
calculate the maximum BG overhead correctly, since it doesn't seem to know
about metabg.

Of course there's the question of whether or not we really /want/ people
formatting 500T ext4 filesystems.  meta_bg is not turned on by default, so
the defaults will still fail unless they know to pass that option.

(Frankly, doing so is probably insane.)


> #
> Cheers,
> Dave.
> -- 
> Dave Chinner
> --
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